O. Fox

University of California, Berkeley, Berkeley, California, United States

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Publications (104)257.73 Total impact

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    ABSTRACT: We present a systematic study of mid-infrared (mid-IR) emission from 141 nearby supernovae (SNe) observed with the InfraRed Array Camera (IRAC) on the Spitzer Space Telescope. These SNe reside in one of the 190 galaxies within 20Mpc drawn from the ongoing three-year SPIRITS program. Both new SPIRITS observations and data from other programs available in the archive are used in this study. We detect 8 Type Ia SNe and 36 core-collapse SNe. All Type I SNe fade and become undetectable within 3 years of explosion. About 22±11% of Type II SNe continue to be detected at late-times with five events detected even two decades after discovery. Dust luminosity, temperature, and mass are obtained by fitting the spectral energy distributions using photometry with IRAC bands 1 and 2. The dust mass estimate is a lower limit as the dust cloud could be optically thick or there could be cooler dust hiding at longer wavelengths. The estimate also does not distinguish between pre-existing and newly produced dust. We observe warm dust masses between 10^(-2) and 10^(-6) M_☉ and dust temperatures from 200K to 1280 K. We present detailed case studies of two extreme Type II-P SNe: SN2011ja and SN 2014bi. SN 2011ja was over-luminous ([4.5] = -15.6 mag) at 900 days post-explosion accompanied by a monotonic growth of the dust mass. This suggests either an episode of dust formation similar to SN 2004et and SN 2004dj, or an intensifying CSM interactions heating up pre-existing dust. SN 2014bi showed a factor of 10 decrease in dust mass over one month suggesting either an episode of dust destruction or a fading source of dust heating. A re-brightening in the mid-IR light curve of the Type Ib SN 2014C coinciding with a rise in the dust mass indicates either an episode of dust production perhaps via CSM interactions or more pre-existing dust getting heated up by the CSM interactions. This observation adds to a small number of stripped-envelope SNe that have mid-IR excess as has been previously reported in the case of SN 2006jc. The observed dust mass and the location of the CSM interactions suggest that the CSM shell around SN 2014C is originated from an LBV-like eruption roughly 100 years before the explosion. We also report detections of SN 1974E, SN 1979C, SN1980K, SN 1986J, and SN 1993J more than 20 years post-explosion. The number of outlying SNe identified in this work demonstrates the power of late time mid-IR observations of a large sample of SNe to identify events with unusual evolution.
    No preview · Article · Jan 2016
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    ABSTRACT: While recent observations provide evidence that super-Chandrasekhar Type Ia supernovae and at least a fraction of normal Type Ia supernovae probably originate from double-degenerate systems, these two subclasses show distinct characteristics observationally. Here we report an intermediate supernova iPTF13asv that may bridge this gap. On the one hand, similar to normal Type Ia supernovae, the over-luminous iPTF13asv follows the empirical relation between the peak magnitude, the lightcurve shape and its intrinsic color, and shows a near-IR secondary maximum like normal supernovae. On the other hand, similar to super-Chandrasekhar events, it has strong UV emission around maximum, low expansion velocities and persistent carbon absorption. We estimate a ^(56)Ni mass of 0.81^(+0.10)_(-0.18) M_☉ and a total ejecta mass of 1.44^(+0.44)_(-0.12) M_☉. Despite these similarities, iPTF13asv lacks iron absorption in its early-phase spectra, indicating a stratified ejecta structure with weak mixing. Based on the strong stratification of the ejecta and the similarity to super-Chandrasekhar events, we infer that iPTF13asv probably originates from a double-degenerate system.
    Preview · Article · Jan 2016
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    ABSTRACT: Supernovae Type Iax (SNe Iax) are less energetic and less luminous than typical thermonuclear explosions. A suggested explanation for the observed characteristics of this subclass is a binary progenitor system consisting of a CO white dwarf primary accreting from a helium star companion. A single-degenerate explosion channel might be expected to result in a dense circumstellar medium (CSM), although no evidence for such a CSM has yet been observed for this subclass. Here we present recent Spitzer observations of the SN Iax 2014dt obtained by the SPIRITS program nearly one year post-explosion that reveal a strong mid-IR excess over the expected fluxes of more normal SNe Ia. This excess is consistent with 1E-5 M_solar of newly formed dust, which would be the first time that newly formed dust has been observed to form in a normal Type Ia. The excess, however, is also consistent with a dusty CSM that was likely formed in pre-explosion mass-loss, thereby suggesting a single degenerate progenitor system. Compared to other SNe Ia that show significant shock interaction (SNe Ia-CSM) and interacting core-collapse events (SNe IIn), this dust shell in SN 2014dt is less massive. We consider the implications that such a pre-existing dust shell has for the progenitor system, including a binary system with a mass donor that is a red giant, a red supergiant, and an asymptotic giant branch star.
    Full-text · Article · Oct 2015
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    ABSTRACT: We present our extensive observational campaign on the Swift-discovered GRB141121A, al- most ten years after its launch. Our observations covers radio through X-rays, and extends for more than 30 days after discovery. The prompt phase of GRB 141121A lasted 1410 s and, at the derived redshift of z = 1.469, the isotropic energy is E{\gamma},iso = 8.0x10^52 erg. Due to the long prompt duration, GRB141121A falls into the recently discovered class of UL-GRBs. Peculiar features of this burst are a flat early-time optical light curve and a radio-to-X-ray rebrightening around 3 days after the burst. The latter is followed by a steep optical-to-X-ray decay and a much shallower radio fading. We analyze GRB 141121A in the context of the standard forward-reverse shock (FS,RS) scenario and we disentangle the FS and RS contributions. Finally, we comment on the puzzling early-time (t ~3 d) behavior of GRB 141121A, and suggest that its interpretation may require a two-component jet model. Overall, our analysis confirms that the class of UL-GRBs represents our best opportunity to firmly establish the prominent emission mechanisms in action during powerful GRB explosions, and future missions (like SVOM, XTiDE, or ISS-Lobster) will provide many more of such objects.
    Full-text · Article · Oct 2015 · The Astrophysical Journal
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    ABSTRACT: Gamma-ray bursts (GRBs) are the most luminous explosions in the universe, yet the nature and physical properties of their energy sources are far from understood. Very important clues, however, can be inferred by studying the afterglows of these events. We present optical and X-ray observations of GRB 130831A obtained by Swift, Chandra, Skynet, RATIR, Maidanak, ISON, NOT, LT and GTC. This burst shows a steep drop in the X-ray light-curve at $\simeq 10^5$ s after the trigger, with a power-law decay index of $\alpha \sim 6$. Such a rare behaviour cannot be explained by the standard forward shock (FS) model and indicates that the emission, up to the fast decay at $10^5$ s, must be of "internal origin", produced by a dissipation process within an ultrarelativistic outflow. We propose that the source of such an outflow, which must produce the X-ray flux for $\simeq 1$ day in the cosmological rest frame, is a newly born magnetar or black hole. After the drop, the faint X-ray afterglow continues with a much shallower decay. The optical emission, on the other hand, shows no break across the X-ray steep decrease, and the late-time decays of both the X-ray and optical are consistent. Using both the X-ray and optical data, we show that the emission after $\simeq 10^5$ s can be explained well by the FS model. We model our data to derive the kinetic energy of the ejecta and thus measure the efficiency of the central engine of a GRB with emission of internal origin visible for a long time. Furthermore, we break down the energy budget of this GRB into the prompt emission, the late internal dissipation, the kinetic energy of the relativistic ejecta, and compare it with the energy of the associated supernova, SN 2013fu.
    No preview · Article · Sep 2015 · Monthly Notices of the Royal Astronomical Society
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    ABSTRACT: SN 2006gy was the most luminous supernova (SN) ever observed at the time of its discovery and the first of the newly defined class of superluminous supernovae (SLSNe). The extraordinary energetics of SN 2006gy and all SLSNe (>1051 erg) require either atypically large explosion energies (e.g. pair-instability explosion) or the efficient conversion of kinetic into radiative energy (e.g. shock interaction). The mass-loss characteristics can therefore offer important clues regarding the progenitor system. For the case of SN 2006gy, both a scattered and thermal light echo from circumstellar material (CSM) have been reported at later epochs (day ∼800), ruling out the likelihood of a pair-instability event and leading to constraints on the characteristics of the CSM. Owing to the proximity of the SN to the bright host-galaxy nucleus, continued monitoring of the light echo has not been trivial, requiring the high resolution offered by the Hubble Space Telescope (HST) or ground-based adaptive optics (AO). Here, we report detections of SN 2006gy using HST and Keck AO at ∼3000 d post-explosion and consider the emission mechanism for the very late-time light curve. While the optical light curve and optical spectral energy distribution are consistent with a continued scattered-light echo, a thermal echo is insufficient to power the K′-band emission by day 3000. Instead, we present evidence for late-time infrared emission from dust that is radiatively heated by CSM interaction within an extremely dense dust shell, and we consider the implications on the CSM characteristics and progenitor system.
    No preview · Article · Sep 2015 · Monthly Notices of the Royal Astronomical Society
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    ABSTRACT: We present extensive optical (UBVRI, g'r'i'z', and open CCD) and near-infrared (ZYJH) photometry for the very nearby Type IIP supernova (SN) 2013ej extending from +1 to +215 days after shock breakout. Substantial time series ultraviolet and optical spectroscopic observations obtained from +8 to +135 days after the explosion are also presented. We use early optical photometry to determine the time of shock breakout to be MJD 56496.9+/-0.3. We calibrate unfiltered CCD observations to pseudo-bolometric UBVRI light curve data of Type IIP supernovae (SNe), obtaining 4% precision with a B-V color-dependent correction. Considering well-observed SNe from the literature, we derive a UBVRIJHK bolometric calibration from the UBVRI measurement to better than 2% precision. We observe moderately strong Si~II {\lambda}6355 as early as 8 days after explosion. We model spectra in the vicinity of Fe~II {\lambda}5169 whenever observed to determine the photospheric velocity, v{\phi}, yielding 4500+/-500 km s^-1 50 days after explosion. We observe similar early ultraviolet spectra at 10--12 days after explosion for SNe~IIP, but see diverse behavior several days earlier. Using the expanding photosphere method, and combining with SN 2002ap, we estimate the host galaxy distance to be 9.0^-0.6_+0.4 Mpc, consistent with estimates from other methods. Photometric and spectroscopic analysis during the plateau phase, which we estimate to be 86+/-6 days long, yields an estimated explosion energy of 1.05+/-0.43 x 10^51 ergs, a total ejected mass of 14.3+/-4.5 MSol, and a pre-supernova radius of 200+/-82 RSol. Measurements from the radioactive tail phase yield a 56Ni mass of 0.019+/-0.001 MSol.
    Full-text · Article · Sep 2015
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    ABSTRACT: We present optical and near-infrared light curves and optical spectra of SN 2013dx, associated with the nearby (redshift 0.145) gamma-ray burst GRB130702A. The prompt isotropic gamma-ray energy released from GRB130702A is measured to be E ;iso = 6:4+1:3
    Full-text · Article · Aug 2015 · The Astrophysical Journal
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    Brian J. Williams · Ori D. Fox
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    ABSTRACT: We present photometric observations from the {\it Stratospheric Observatory for Infrared Astronomy (SOFIA)} at 11.1 $\mu$m of the Type IIn supernova (SN IIn) 2010jl. The SN is undetected by {\it SOFIA}, but the upper limits obtained, combined with new and archival detections from {\it Spitzer} at 3.6 \& 4.5 $\mu$m allow us to characterize the composition of the dust present. Dust in other Type IIn SNe has been shown in previous works to reside in a circumstellar shell of material ejected by the progenitor system in the few millenia prior to explosion. Our model fits show that the dust in the system shows no evidence for the strong, ubiquitous 9.7 $\mu$m feature from silicate dust, suggesting the presence of carbonaceous grains. The observations are best fit with 0.01-0.05 $\msun$ of carbonaceous dust radiating at a temperature of $\sim 550-620$ K. The dust composition may reveal clues concerning the nature of the progenitor system, which remains ambiguous for this subclass. Most of the single star progenitor systems proposed for SNe IIn, such as luminous blue variables, red supergiants, yellow hypergiants, and B[e] stars, all clearly show silicate dust in their pre-SN outflows. However, this post-SN result is consistent with the small sample of SNe IIn with mid-IR observations, none of which show signs of emission from silicate dust in their IR spectra.
    Preview · Article · Jun 2015
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    ABSTRACT: SN 2013dy is a Type Ia supernova (SN Ia) for which we have compiled an extraordinary data set spanning from 0.1 to ∼ 500 d after explosion. We present 10 epochs of ultraviolet (UV) through near-infrared (NIR) spectra with Hubble Space Telescope/Space Telescope Imaging Spectrograph, 47 epochs of optical spectra (15 of them having high resolution), and more than 500 photometric observations in the BVrRiIZYJH bands. SN 2013dy has a broad and slowly declining light curve (Δm15(B) = 0.92 mag), shallow $\mathrm{Si}\,\small {II}\,\lambda 6355$ absorption, and a low velocity gradient. We detect strong C ii in our earliest spectra, probing unburned progenitor material in the outermost layers of the SN ejecta, but this feature fades within a few days. The UV continuum of SN 2013dy, which is strongly affected by the metal abundance of the progenitor star, suggests that SN 2013dy had a relatively high-metallicity progenitor. Examining one of the largest single set of high-resolution spectra for an SN Ia, we find no evidence of variable absorption from circumstellar material. Combining our UV spectra, NIR photometry, and high-cadence optical photometry, we construct a bolometric light curve, showing that SN 2013dy had a maximum luminosity of $10.0^{+4.8}_{-3.8} \times 10^{42}$ erg s−1. We compare the synthetic light curves and spectra of several models to SN 2013dy, finding that SN 2013dy is in good agreement with a solar-metallicity W7 model.
    Preview · Article · Apr 2015 · Monthly Notices of the Royal Astronomical Society
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    ABSTRACT: We present medium resolution near-infrared (NIR) spectra, covering 1.1 to 3.4 microns, of the normal Type Ia supernova (SN Ia) SN 2014J in M82 obtained with the FLITECAM instrument aboard SOFIA approximately 17-25 days after maximum B light. Our 2.8-3.4 micron spectra may be the first ~3 micron spectra of a SN Ia ever published. The spectra spanning the 1.5-2.7 micron range are characterized by a strong emission feature at ~1.77 microns with a full width at half maximum of ~11,000-13,000 km/s. We compare the observed FLITECAM spectra to the recent non-LTE delayed detonation models of Dessart et al. (2014) and find that the models agree with the spectra remarkably well in the 1.5-2.7 micron wavelength range. Based on this comparison we identify the ~1.77 micron emission peak as a blend of permitted lines of Co II. Other features seen in the 2.0 - 2.5 micron spectra are also identified as emission from permitted transitions of Co II. However, the models are not as successful at reproducing the spectra in the 1.1 - 1.4 micron range or between 2.8 and 3.4 microns. These observations demonstrate the promise of SOFIA by allowing access to wavelength regions inaccessible from the ground, and serve to draw attention to the usefulness of the regions between the standard ground-based NIR passbands for constraining SN models.
    Full-text · Article · Mar 2015 · The Astrophysical Journal
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    ABSTRACT: We present optical and near-infrared (NIR) photometry of 28 gamma-ray bursts (GRBs) detected by the Swift satellite and rapidly observed by the Reionization and Transients Infrared/Optical (RATIR) camera. We compare the optical flux at fiducial times of 5.5 and 11 h after the high-energy trigger to that in the X-ray regime to quantify optical darkness. 46 ± 9 per cent (13/28) of all bursts in our sample and 55 ± 10 per cent (13/26) of long GRBs are optically dark, which is statistically consistently with previous studies. Fitting RATIR optical and NIR spectral energy distributions of 19 GRBs, most (6/7) optically dark GRBs either occur at high redshift (z > 4.5) or have a high dust content in their host galaxies (AV > 0.3). Performing Kolmogorov–Smirnov tests, we compare the RATIR sample to those previously presented in the literature, finding our distributions of redshift, optical darkness, host dust extinction and X-ray-derived column density to be consistent. The one reported discrepancy is with host galaxy dust content in the BAT6 sample, which appears inconsistent with our sample and other previous literature. Comparing X-ray-derived host galaxy hydrogen column densities to host galaxy dust extinction, we find that GRBs tend to occur in host galaxies with a higher metal-to-dust ratio than our own Galaxy, more akin to the Large and Small Magellanic Clouds. Finally, to mitigate time evolution of optical darkness, we measure βOX, rest at a fixed rest-frame time, trest = 1.5 h and fixed rest-frame energies in the X-ray and optical regimes. Choosing to evaluate optical flux at λrest = 0.25 μm, we remove high redshift as a source of optical darkness, demonstrating that optical darkness must result from either high redshift, dust content in the host galaxy along the GRB sight line, or a combination of the two.
    Full-text · Article · Dec 2014 · Monthly Notices of the Royal Astronomical Society
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    ABSTRACT: SN 2014J in M82 is the closest Type Ia supernova (SN Ia) in decades. The proximity allows for detailed studies of supernova physics and provides insights into the circumstellar and interstellar environment. In this work we analyze Spitzer mid-IR data of SN 2014J in the 3.6 and 4.5 {\mu}m wavelength range, together with several other nearby and well-studied SNe Ia. We compile the first composite mid-IR light-curve templates from our sample of SNe Ia, spanning the range from before peak brightness well into the nebular phase. Our observations indicate that SNe Ia form a very homogeneous class of objects at these wavelengths. Using the low-reddening supernovae for comparison, we constrain possible thermal emission from circumstellar dust around the highly reddened SN 2014J. We also study SNe 2006X and 2007le, where the presence of matter in the circumstellar environment has been suggested. No significant mid-IR excess is detected, allowing us to place the most constraining upper limits to date on the amount of pre-existing dust in the circumstellar environment of any SN Ia. For SN 2014J, $M_{dust} < 10^{-5}$ M$_{\odot}$ within $r_{dust} \sim 10^{17}$ cm, which is insufficient to account for the observed extinction. Similar limits are obtained for SNe 2006X and 2007le.
    Full-text · Article · Nov 2014
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    ABSTRACT: KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among the brightest active galaxies monitored by the Kepler mission. We have carried out a reverberation mapping campaign designed to measure the broad-line region size and estimate the mass of the black hole in this galaxy. We obtained 74 epochs of spectroscopic data using the Kast Spectrograph at the Lick 3-m telescope from February to November of 2012, and obtained complementary V-band images from five other ground-based telescopes. We measured the H-beta light curve lag with respect to the V-band continuum light curve using both cross-correlation techniques (CCF) and continuum light curve variability modeling with the JAVELIN method, and found rest-frame lags of lag_CCF = 13.53 (+2.03, -2.32) days and lag_JAVELIN = 13.15 (+1.08, -1.00) days. The H-beta root-mean-square line profile has a width of sigma_line = 770 +/- 49 km/s. Combining these two results and assuming a virial scale factor of f = 5.13, we obtained a virial estimate of M_BH = 8.06 (+1.59, -1.72) x 10^6 M_sun for the mass of the central black hole and an Eddington ratio of L/L_Edd ~ 0.2. We also obtained consistent but slightly shorter emission-line lags with respect to the Kepler light curve. Thanks to the Kepler mission, the light curve of KA1858+4850 has among the highest cadences and signal-to-noise ratios ever measured for an active galactic nucleus; thus, our black hole mass measurement will serve as a reference point for relations between black hole mass and continuum variability characteristics in active galactic nuclei.
    Full-text · Article · Aug 2014 · The Astrophysical Journal
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    ABSTRACT: A growing subset of Type Ia supernovae (SNe Ia) show evidence for unexpected interaction with a dense circumstellar medium (SNe Ia-CSM). The precise nature of the progenitor, however, remains debated owing to spectral ambiguities arising from a strong contribution from the CSM interaction. Late-time spectra offer potential insight if the post-shock cold, dense shell becomes sufficiently thin and/or the ejecta begin to cross the reverse shock. To date, few high-quality spectra of this kind exist. Here we report on the late-time optical and infrared spectra of the SNe Ia-CSM 2012ca and 2013dn. These SNe Ia-CSM spectra exhibit low [Fe III]/[Fe II] ratios and strong [Ca II] at late epochs. Such characteristics are reminiscent of the super-Chandrasekhar-mass (SC) candidate SN 2009dc, for which these features suggested a low-ionisation state due to high densities, although the broad Fe features admittedly show similarities to the blue “quasi-continuum” observed in some core-collapse SNe Ibn and IIn. Neither SN 2012ca nor any of the other SNe Ia-CSM show evidence for broad oxygen, carbon, or magnesium in their spectra. Similar to the interacting Type IIn SN 2005ip, a number of high-ionisation lines are identified in SN 2012ca, including [S III], [Ar III], [Ar X], [Fe VIII], [Fe X], and possibly [Fe XI]. The total bolometric energy output does not exceed 10^(51) erg, but does require a large kinetic-to-radiative conversion efficiency. All of these observations taken together suggest that SNe Ia-CSM are more consistent with a thermonuclear explosion than a core-collapse event, although detailed radiative transfer models are certainly necessary to confirm these results.
    Preview · Article · Aug 2014 · Monthly Notices of the Royal Astronomical Society
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    ABSTRACT: The well-studied Type IIn supernova (SN) 1998S is often dubbed the prototypical SN IIn, and it provides a unique opportunity to study its progenitor star from within as the object lights up dense circumstellar material (CSM) launched from the star before it underwent core collapse. In this article we present a Keck HIRES spectrum of SN 1998S taken within a few days after shock breakout -- both the earliest high-resolution spectrum published of a SN IIn and the earliest published spectrum of SN 1998S. Our analysis indicates that the inner CSM displays qualitatively different properties from the outer CSM, perhaps owing to a change in the mass-ejection properties of the progenitor ~10 yr before core collapse. Modern SN studies achieve remarkably short turnaround times between the SN shock breakout and the first observed spectrum, but high-resolution spectra of very young SNe are rare; the unique spectrum presented here provides a useful case study for observations of other young SN systems, including SN 2013cu, which displayed a remarkably similar spectrum when very young. We examine the fully resolved emission-line profiles of SN 1998S to ascertain the composition, density, and velocity gradients within the CSM, finding evidence for extreme (and short-lived) mass loss at velocities much less than those characteristic of Wolf-Rayet (WR) stars. A comparison with a spectrum of SN 2013cu indicates similar sub-WR velocities, suggesting that its progenitor was also not a WR star.
    Preview · Article · Aug 2014 · The Astrophysical Journal
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    ABSTRACT: SN 2014J in M82 is the closest detected Type Ia supernova (SN Ia) in at least 28 yr and perhaps in 410 yr. Despite its small distance of 3.3 Mpc, SN 2014J is surprisingly faint, peaking at V = 10.6 mag, and assuming a typical SN Ia luminosity, we infer an observed visual extinction of AV = 2.0 ± 0.1 mag. But this picture, with RV = 1.6 ± 0.2, is too simple to account for all observations. We combine 10 epochs (spanning a month) of HST/Space Telescope Imaging Spectrograph (STIS) ultraviolet through near-infrared spectroscopy with HST/Wide Field Camera 3 (WFC3), Katzman Automatic Imaging Telescope, and FanCam photometry from the optical to the infrared and nine epochs of high-resolution TRES (Tillinghast Reflection Echelle Spectrograph) spectroscopy to investigate the sources of extinction and reddening for SN 2014J. We argue that the wide range of observed properties for SN 2014J is caused by a combination of dust reddening, likely originating in the interstellar medium of M82, and scattering off circumstellar material. For this model, roughly half of the extinction is caused by reddening from typical dust (E(B − V) = 0.45 mag and RV = 2.6) and roughly half by scattering off Large Magellanic Cloud-like dust in the circumstellar environment of SN 2014J.
    No preview · Article · Aug 2014 · Monthly Notices of the Royal Astronomical Society
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    ABSTRACT: The origin of dust in galaxies is still a mystery. The majority of the refractory elements are produced in supernova explosions but it is unclear how and where dust grains condense and grow, and how they avoid destruction in the harsh environments of star-forming galaxies. The recent detection of 0.1-0.5 solar masses of dust in nearby supernova remnants suggests in situ dust formation, while other observations reveal very little dust in supernovae the first few years after explosion. Observations of the bright SN 2010jl have been interpreted as pre-existing dust, dust formation or no dust at all. Here we report the rapid (40-240 days) formation of dust in its dense circumstellar medium. The wavelength dependent extinction of this dust reveals the presence of very large (> 1 micron) grains, which are resistant to destructive processes. At later times (500-900 days), the near-IR thermal emission shows an accelerated growth in dust mass, marking the transition of the supernova from a circumstellar- to an ejecta-dominated source of dust. This provides the link between the early and late dust mass evolution in supernovae with dense circumstellar media.
    Full-text · Article · Jul 2014 · Nature
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    ABSTRACT: We present a template-fitting algorithm for determining photometric redshifts, z phot, of candidate high-redshift gamma-ray bursts (GRBs). Using afterglow photometry, obtained by the Reionization and Transients InfraRed (RATIR) camera, this algorithm accounts for the intrinsic GRB afterglow spectral energy distribution, host dust extinction, and the effect of neutral hydrogen (local and cosmological) along the line of sight. We present the results obtained by this algorithm and the RATIR photometry of GRB 130606A, finding a range of best-fit solutions, 5.6 < z phot < 6.0, for models of several host dust extinction laws (none, the Milky Way, Large Magellanic Clouds, and Small Magellanic Clouds), consistent with spectroscopic measurements of the redshift of this GRB. Using simulated RATIR photometry, we find that our algorithm provides precise measures of z phot in the ranges of 4 < z phot 8 and 9 < z phot < 10 and can robustly determine when z phot > 4. Further testing highlights the required caution in cases of highly dust-extincted host galaxies. These tests also show that our algorithm does not erroneously find z phot < 4 when z sim > 4, thereby minimizing false negatives and allowing us to rapidly identify all potential high-redshift events.
    Full-text · Article · May 2014 · The Astronomical Journal
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    ABSTRACT: The Type IIb supernova (SN) 1993J is one of only a few stripped-envelope SNe with a progenitor star identified in pre-explosion images. SN IIb models typically invoke H envelope stripping by mass transfer in a binary system. For the case of SN 1993J, the models suggest that the companion grew to 22 M ☉ and became a source of ultraviolet (UV) excess. Located in M81, at a distance of only 3.6 Mpc, SN 1993J offers one of the best opportunities to detect the putative companion and test the progenitor model. Previously published near-UV spectra in 2004 showed evidence for absorption lines consistent with a hot (B2 Ia) star, but the field was crowded and dominated by flux from the SN. Here we present Hubble Space Telescope Cosmic Origins Spectrograph and Wide-Field Camera 3 observations of SN 1993J from 2012, at which point the flux from the SN had faded sufficiently to potentially measure the UV continuum properties from the putative companion. The resulting UV spectrum is consistent with contributions from both a hot B star and the SN, although we cannot rule out line-of-sight coincidences.
    Preview · Article · May 2014 · The Astrophysical Journal

Publication Stats

720 Citations
257.73 Total Impact Points

Institutions

  • 2013-2015
    • University of California, Berkeley
      • Department of Astronomy
      Berkeley, California, United States
  • 2008-2013
    • NASA
      Вашингтон, West Virginia, United States
  • 2006-2011
    • University of Virginia
      • Department of Astronomy
      Charlottesville, VA, United States